Process for removing condensates from gas



Aug. 19, 1941. H. J. sToEvER 2,252,739

PROCESS FOR REMOVING CONDENSATES FROM GAS Filed oct. 18, 1958 @AG/@1MM Patented Aug. 19, 1941 UNITED STATES PATENT-"OFFICE Y l 'Y :,zszsss Herman .1. Stoever, Ames, Iowa, assigner to The United Gal Improvement Company, a tion of Pennsylvania appueeaon october 1s, 193s. 4sulla Ne. 235.693

This invention pertains generally to the re` 'moval of condensible materials from gas. and pers claims. (ci. swims) I1 of heat exchanger Ill. and line Il is connected to the inlet of uid space Il of heat exchanger I2.

tains .particularly to the recovery of' valuable'V hydrocarbons from manufactured gas such as carburetted water gas, oil gas, coal gas, etc., although it is equally applicable to natural gas.

It is well known that condensible vapors may be removed from manufactured gas by lowering the temperature of the gas. It is found, however, that the gas contains certain materials which solidify or freeze at low temperatures necessary to remove substantial quantities of the more valuable hydrocarbons. v

Examples of materials which solidify or freeze are water and benzol.

As a result of the freezing of certain of the materialsl contained in the gas a gradual stopping up of'the gas passsages occurs due to the accumulation of frost. 'I'hese accumulations not only interfere with eillcient heat transfer, but eventually stop up the equipment.

It has been proposed to duplicate the gas cooling system and to alternately operate one system while the other is being thawed out.

A feature of this invention resides in alternately thawing out such systems without loosing the refrigeration stored up in the frost, in the cold metal, etc.

A further feature of the invention resides in the continuous lowering of the temperature of a v gas to abstract condensibles therefrom.

A further feature of the invention resides in the eillcient use of refrigeration in condensing materials from a gas. l

A further feature of the invention resides in an efficient, simple and commercially feasible method for accomplishing the purpose intended.

Further features of the invention reside in the construction, arrangement and combinations of parts, and in the steps, combinations of steps vand sequences of steps, all of which together with other features will become more apparent to persons skilled in the art as the specification proceeds. and upon reference to the drawing in which: u

Figure 1 is a ilow'sheet illustrating one form of the invention; and I Figure 2 is a flow sheet illustrating another form'of the invention.

Referring now more particularly to Figure 1, Il, I I, I2, and Il are heat exchangers.

Il is a gas supply line leading from a source of gas to be treated (not shown).

Line Il branches into lines I5 and Ii.

Line I! is connected to the inlet of fluid space The outlet of fluid space I1 is connected by line ItA to the inlet of fluid space 2II of heat exchanger II, and the outlet of duid space Il is connected by line 2I to the inlet of fluid space 22 of heat exchanger I3.

The outlet of fluid space 20 is connected to line 2l which divides into lines r2l and 25.

Line 2l leads to the inlet of uid space 2i of heat exchanger Il, the outlet of which is connected to line 21 which leads to a holder for nished gas, not shown.

Lin 26, on the other hand. connects with line 2 The outlet of fluid space 22 of heat exchanger Lines 24, 25, 29, and 2l are provided with valves l5, 28, 21 and 38 respectively.

Fluid space of heat exchange I I is connected across a supply of refrigerant. not shown.

Likewise, fluid space Il of heat exchanger Il is connected across a supply of refrigerant, not

shown.

Indescribing the operation of the apparatus shown in Figure 1, let it be assumed that valves I6, and 31 are open and valves 38 and 28 closed, that heat exchangers I2 and Il are frosted up and that heat exchangers III and I I are defrosted. Valve 5I is open and valve $2 closed.

The incoming relatively warm gas to be treated flows through line Il and divides between lines I! and II according to the relative openings of valves I! and 31.

The gas flowing through line I5 flows through fluid space I1, line III, fluid space 20, line 23, line 2l, fluid space 28, and line 21 to` storage.

As this gas flows through fluid space I1. it is space 22, line 28 and then line 28 from which the vgas thus pre-cooled enters into line I8.

The flow of gas through the circuit between line I8 and line I8 is sufficient to adequately defrost heat exchangers I2 and I8,`and the liquid thus produced is drawn ot! through lines 41 and 48 respectively.' Flow in line 41 is controlled by valve 48,

and flow in/line 48 is controlled by valve 58.

Thus cold stored up in heat exchangers i2 and I8 is Venlciently recovered and at the same time heat exchangers I2 and I8 are defrosted.

As the process proceeds heat exchangers I8 and Due to thecold supplied by the refrigerant flowing through fluid space 48, the gas leaves fluidspace 28 at -80" F., enters fluid space 28 at this temperature, and leaves fluid space 28 at 60 F. at which temperature it is delivered tov l* storage.

During lthe other part of the cycle, namely,

when valves 85 and 31 are closed and valves 88 II eventually become frosted up whereupon valves 88 and 88 are' opened and valves 85 and 81 closed. Valve 5I is now closed and valve 52 opened.

The incoming gasv still divides between lines I5 and I8, but the relative amounts are no longer determined by the relative openings of valves 85 and 81, but by the relative openings of valves 88 and 88.

That portion of the gas which flows through line I8 enters duid space I8 wherein it is precooled by the cold treated gas flowing through :duid space 8| to storage. From fluid space I8 the gas flows through line 2| into fluid space 22 wherein it is cooled by refrigerant flowing' and 88 are open, the-.same temperatures apply but to the alternate parts of the system.

It will be understood, of course, that the temperatures given are hardly more than rough apiroximations and are merely by way of explana ion.

Referring now to Figure 2, line 55 for incoming gas is connected to a supply, not shown.

Line 55 divides between lines 58 and 51 which lead to fluid spaces 58 and 58 of heat exchangers 80 and 8i respectively.

The outlets of fluid spaces 58 vand 58 are connected to lines 82 and 88 respectively, which lead to a common outlet line 84 which, in turn, may

lead to a suitable point such as a holder, not shown.

Lines 58 and 51 are connected by a line 85 and lines 82 and 88 are connected by a line. 88. Line through fluid space 4I, valve 52 having been opened for this purpose.

The cooled gas'ows out through line 28, line 88, fluid space 8|, line 82 and line 21 to storage. Condensate produced in fluid space I8 is drawn oil.' 'through line 41, and condensate produced in uid space 22 is drawn oif'through line 48.

That portion of the gas which flows through line I5 flows through fluid space I1, line I8, fluid space 20, line 28 and line 25 from which the precooled gas enters line 2|. The flow of gas through the circuit between line I5 and line 2| is sumcient to adequately defrost heat exchangers I8 and II, and the liquid thus produced is drawn od' through lines 48 and 45 respectively.

When heat exchangers I2 and I 8 become frosted up the above cycle is repeated.

By this means the cold .stored up in the frost and in the metal of heat exchangers requiring defrosting is substantially completely' ecovered along with the materials making up e frost.

It will be seen that the temperatures at various points in the system are subject to considerable variation, if desired or required.' Therefore, the following is to be considered as merely illustrative.

The incoming gas may enter at say '70 F.

'through une u.

Let us assume that heat exchangers I8 and II are on the gas cooling part of the cycle, and heat exchangers I2 and I8 on the Adefrosting part of the cycle. Thus valves 85 and 81 will be open and valves 88 and 58 closed. Valve'5I will be open and valve 52 closed.

The gas enters fluid space I1 through line I5 at 10 F.. and leaves fluid space I1 at 0 F.

Gas enters fluid space I8 through line I8 at '70 F., leaves uid space I8 at 60 F., enters fluid space 22 at 60 F.. leaves fluid space 22 at 10 F., and enters line I8 at 10 F.

Due tothe difference in temperature of the gas entering line I8 from fluid space I1, and the gas entering line I8 from fluid space 22, the gas entering iiuid space 28 is at 5 F.

85 at an intermediate point 81 and line 88 at an intermediate point 88 are connected by line 8'8.

Line 58 is provided with a valve 1I, line 51 with a valve 12, line 85 on opposed sides of intermediate point 81 with valves 18 and 14, line 88 on opposed sides of intermediate point 88 with valves 15 and 18, line 88 with valve 11, and line 82 with valve 18.

Fluid space 18 of heat, exchanger 80 is connected across a refrigerant Supply notfshown, the dow of refrigerant being controlled by valve 88, and fluid space 82 of heat exchanger 8| is connected across a refrigerant supply not shown, the

ilow of refrigerant being controlled by valve 8 8.

Liquid is drained from fluid space 58 through line 84 and liquid is withdrawn from fluid space 58 through line 85.

The operation of the apparatus shown in Figure 2 is as follows:

Let it be assumed that the system has been "operating and that heat exchanger 88 has becomefrosted up.

During suchoperation, which resulted in the frosting up of heatV exchanger 80, all of the even numbered valves were open and all of the odd numbered valves closed. Consequently, the incoming gas flowed through line 12, uid space 58, line 83, line 88, line 89, line 85, line 58, fluid space 88, line 82 to vline 84. The warm gas upon passing through fluid space 58 removed any frost therein, the liquid being drained through line 85.

Pre-cooled gas entered fluid ,space 58 wherein it was further cooled by the flow of refrigerant through fluid space 18, the condensate being removed through line v84. The finished gas passed oil' through line 82 and line 84 to storage.

To .defrost heat exchanger 80, the even numfbered valves are closed and the odd numbered valves opened, whereupon the incoming warm gas flows through line 58, iluidspace 58 to melt the frost, line 82, line 88, line 88, line 85, fluid space 58, wherein it is further cooled by refrigthe `frosted heat exchanger is thawed Aout withouta loss in refrigeration.

- Itfis, of course, to be understood that the gas iiowing out through line Il might be brought into heat exchange relationship with any suitable fluid for recovering the cold therein, for instance,

with the incoming las. Y e

A It will be seen that the temperatures throughout this form of the invention might be controlled more or less at will. Therefore, the

following is merely illustrative. .The wma! enter the system through line Il at say -2012 Assuming that the odd numbered Iprovide a reduced temperature for gas flowing to line ll.\

When the odd numbered valves are closed and the even numbered valves are open, the temperatures in the above illustration are, of course, reversed in the system. i

By Athe practice of my invention the most troublesome difiiculty in the recovery of gas constituents by refrigeration is eiliciently and eectively removed without resort to complicated apparatus or involved operations.

-The system lends itself to considerable variations,both as to constructionand operation, and as to the temperatures obtained at various points.

For instance, while the cold treated Zas is normally passed alternately through fluid spaces 2l and Il to recover the cold therefrom, any other refrigerant might be utilized in these iluid spaces, and the treated gas may be sent to storcold there- Athat is the refrigerant in the defrosting heat exchanger might be partly on-stream particularly if this does not prevent defrosting.

Moreover, in Figure 2 when the odd numbered valves are open and the even numbered valves closed, so that the gas first passes through heat exchanger t and then through heat exchanger Il, valve i2 also might be opened to any desired extent so that a part of the gas will ow directly to heat exchanger ti.

Likewise, when the even numbered valves are open and the odd numbered valves closed, valve 1i might be opened to any desired extent so that a part of the incoming gas is conducted directly to heat exchanger Sii.

It is, of course, understood that the invention is adapted to the use of any desired number of heat exchangers, the number shown and more 3v srscuiarly described hungry way of inusuarmmtne foregoing a wm be seen mit a runasl mental feature of invention common to the two forms more particularly described, resides in the gas to be treated serially. through a plurality of heat exchangers having cooling means, said heat exchangers being divided into two portions, said gas passing through said portions with each portion alternately upstream and downstream of gas i'iowin said series, and operating the cooling means of said portions at normal load only when said portions are in downstream position. in said series. thus permitting the incoming gas to thaw frost in said portions when4 said portions are in upstream 'position in'said series.

Another fundamental feature of invention common tothe two forms particularly described, resides in passing the gas to be treated through two series of heat exchangers connected in parallel, saidheat exchangers having gas cooling means, dividing said gas between the two series of heat exchangers, alternately operating the cooling means in said two series of heat exchangers at normal load, and conducting the gas from the terminal of each series of heat exchangers when its cooling means is not operating at normal load to an upstream point of the other series of heat exchangers. f

- It is to be 'understood that the above description-.eis by'rw'ay of illustration and that changes, omissions, additions. substitutions, and/or modi- V flcations might ybe made within the scope of the `claims without departing from the spirit of the invention which is intended to be limited only as required by the prior art.

Iclaim:

l. A process for removing condensible materials from a gas by the reduction in temperature of said gas, said gas `containing a component which solidiiles at the. temperature employed, comprising dividing said gas into two streams, passing each stream through separate heat exchange means having gas-cooling means while alternately combining each of said streams after leaving its respective heat exchange means with the other-of said streams before the passage of said other stream through its respective heat exchange means, and operating the cooling means of each heat exchange means at a temperature sufilciently low to cause 'solidlcation of a gas component only when the combined streams pass therethrough.

2. A `process for removing condensible materials from a gas by the reduction in temperature of said gas, said gas containing a component which solidies at the temperature employed, comprising dividing said gas into two streams, passing each stream through a separate heatexchanger having gas cooling means while alternately combining each of said streams after leaving its respective heat exchanger with the other of said streams adjacent the entry of said other stream into its respective heat exchanger, and operating the cooling means of .each heat exchanger at a temperature suiiiciently low to cause solidication of a gas component only when the combined streams pass therethrough.

which solidiiles at the temperature employed,

comprising dividing said gas into two streams, passing each stream through rseparate heat exchange means having gas cooling means while alternately combining each of said streams after leaving itsjrespective heat exchange means with the other ofsaid streams before the passage of said other streamr through its respective heat exchange means,4 and, operating the cooling means of each heatvexchange means only` when the combined streams pass therethrough.

t. A process for removing condensible materials from a gas by the reduction inytempefrature of said gas, said gas containing a component which solidiiies at the temperature employed, comprising dividing said gas into two streams, passing each stream through separate heat exchange means having cooling means while a1- ternately combining each of said streams after leaving its respective heat exchange means with the other of said streams before the passage oi said other stream through its respective heat exchange means, operating the cooling means of each heat exchange means ata temperature suiliciently low to' cause solidifloation of a gas component only when the combined streams pass therethrough, and bringing "the relatively cold treated gas into heat exchange relationship withkrelatively warmer incoming gas.`

5. A process for removing condensible materials froml a gas by cooling said gas, said gas containing materials which produce a frost at the temperatures employed, comprising passing said gas throughtwo series of heat exchangers connected in parallel, said heatexchangers having'` gas cooling means, said gas dividing between said two series oi heat exchangers, alternately operating the cooling means in said two series of heat exchangers at normal load, and conducting' the gas from the terminal of each series of heat exchangers when its cooling means is not said two series of heat exchangers, alternately' operating and shutting ofi the cooling means in said two series ot heat exchangers, and conducting the gas from the terminal of each 'series oi' `heat exchangers when its cooling means is shut oi to an intermediate Lpoint ofthe other series v o1' heat exchangers.

A 7. A processvfor removing condensiblematerials from a gas-by cooling said gas, said gas containing materials" which produce a frost a the temperatures employed, comprising passing said gas through two series of heat exchangers connected in parallel, said heat exchangers having gas cooling means, said gas dividing between said two series of heat exchangers, alternately operating the cooling means in said two series of heat exchangersat normal load, conducting thegas from the terminal of each series of heat exchangerswhen its cooling means is not operating at normal load to an up-stream point of the other series of heat exchangers, and supplying a part of the refrigeration for cooling -incoming gas by conducting the gas from the terminal of each series ofheat exchangers when its' cooling means is operating at normal load back to a heat exchanger earlier in said seriesl '.,temperatures employed, comprising passing said operating at normal load to an up-stream point of the other series of heat exchangers.

6.A process for. `removing kcondensible materials from a gas by cooling said gas, said gas containing materials which produce a frost at the temperatures employed, comprising passing said gas through two series of heat exchangers connected in parallel, said heat exchangers havinggas cooling means, said gas dividing between gas through two series of heat exchangers` connected in parallel, said heat exchangers having gas cooling means, said gas dividing between said two series of heat exchangers, alternately operating and shutting oif the cooling meansin said two series of heat exchangers, conducting the gas from the terminal of each series of'heat exchangers whenv its cooling means is shut oi! to an intermediate point of the other series of heat exchangers, and supplying a part of the refrigeration for cooling incoming gas by conducting the gas from the terminal of each series of heat exchangers when its cooling means is operating back to a heat exchanger earlier in said series for heat exchange with incoming gas.

HERMAN J. STOEVER. 

